The effect of grape seed extract on cardiovascular risk markers: a meta-analysis of randomized controlled trials

Recent animal studies have suggested that grape seed extract has beneficial effects on the cardiovascular system. Randomized trials in human beings have yielded conflicting results. The objective of this systematic review was to assess the effect of grape seed extract on changes in blood pressure, heart rate, lipid levels, and C-reactive protein (CRP) levels. We searched MEDLINE (January 1, 1950, through October 31, 2010), Agricola (January 1, 1970, through October 31, 2010), Scopus (January 1, 1996, through October 31, 2010), and the Cochrane Central Register of Controlled Trials (through October 31, 2010) for randomized controlled trials in human beings of grape seed extract reporting efficacy data on at least one of the following end points: systolic or diastolic blood pressure, heart rate, total cholesterol, low-density or high-density lipoprotein cholesterol, triglycerides, or CRP. A manual search of references from primary and review articles was performed to identify additional relevant trials. For all endpoints except CRP, the mean change in each parameter from baseline was treated as a continuous variable and the effect size was calculated as the weighted mean difference between the means in the grape seed extract and control groups. Data on CRP were pooled as a standardized mean difference. Nine randomized, controlled trials (N=390) met the inclusion criteria, and a meta-analysis was conducted. Upon meta-analysis, grape seed extract significantly lowered systolic blood pressure (weighted mean difference -1.54 mm Hg (95% confidence interval -2.85 to -0.22, P=0.02]), and heart rate (weighted mean difference -1.42 bpm (95% confidence interval -2.50 to -0.34, P=0.01]). No significant effect on diastolic blood pressure, lipid levels, or CRP was found. No statistical heterogeneity was observed for any analysis (I(2)<39% for all). Egger's weighted regression statistic suggested low likelihood of publication bias in all analysis (P>0.05 for all), except for the effect on diastolic blood pressure (P=0.046). Based on the currently available literature, grape seed extract appears to significantly lower systolic blood pressure and heart rate, with no effect on lipid or CRP levels. Larger randomized, double-blinded trials evaluating different dosages of grape seed extract and for longer follow-up durations are needed.